It's always interesting to see one author write in another's world. That's what's happening here; despite his top billing on the cover, Marc Zicree's only contribution to Angelfire was the world and overall story it takes place in - all the writing is Bohnhoff's.
Bohnhoff fits her story well into the continutity set up in Magic Time, adding new layers to this twisted version of the US. Her locations are imaginative, and the new characters sympathetic - as in the first book, none so much as the ones who aren't quite human anymore. She also does an admirable job of adding depth to the main characters - particularly Colleen, who I was glad to see shake off the tough, masculine stereotype she embodied in the first book. There are some genuine relationships, friendly and un-, cropping up between the questers, too.
Much of this development comes from Bonhoff's use of a first-person viewpoint that rotates between the four main characters. This technique, a significant change from Magic Time, is at best a mixed blessing. While first-person storytelling allows for useful insight into the protagonists' characters, it abandons two of the elements of the first book that I enjoyed.
First, there is very little insight into the minds of the "tweaked" humans, since Bonhoff, unlike Zicree and Hambly, chose not to use them as viewpoints. In Magic Time, those viewpoints provided not only the most interesting characters in the book, but a perspective on "the Change" that was refreshingly -not- that of a normal person in a world gone mad (which, let's face it, aren't that hard to come by). Cal and co. are deeper this time around, but they're not nearly as interesting as what we were shown in the first installment, and the cast feels generic without the inclusion of the series' most inventive aspect.
Second, relegating the storytelling to a tight-knit group means that there's no hint of events outside of their personal experiences. Magic Time left a few threads dangling with regards to the country as a whole, and Angelfire doesn't even acknowledge them. Most supporting characters from the first book have ceased to exist, and the remainder have only references in the dialogue, not actual appearances.
You'll notice that I haven't said much about the actual plot. That's because there's not much to say. It starts well enough, and development for the protagonists is well-done, but there's not much happening other than character growth and introduction up through the middle of the book. And once the climax comes, it's stocked with cliches and almost aggressively predictable. To top it off, there's next to nothing in the way of new information about the series' presumed villain, the power called "Source". Fortunately, Bonhoff's pacing and characterization keep the writing interesting, but the plot is disappointingly generic all around.
If you liked the beginning of Zicree's series, Angelfire is worth the read. Just don't expect the expansiveness of the first book - Magic Time was about the world as much as its characters, but Angelfire is first and foremost a quest story.